The present invention relates to a method for the preparation of a polycarbonate powder or, more particularly, to a method for the preparation of a polycarbonate powder having a large bulk density and a fine and uniform particle size distribution from a solution of the resin.
Known methods in the prior art for the preparation of a polycarbonate powder from a solution of the resin include a method by using a double-screw kneader having a set of spiral blades for material transfer in a direction and a second set of spiral blades for material transfer in a reverse direction disclosed in Japanese Patent Publication No. 53-15899 and a method for the pulverization of the resin by using a poor solvent for the resin disclosed in Japanese Patent Kokai No. 49-28642.
The former method is disadvantageous because the polycarbonate powder obtained by this method has a relatively large particle size sometimes necessitating subsequent pulverization in a down-stream process in order to facilitate drying. The latter method is also disadvantageous in respect of the low bulk density of the powder to cause a problem in obtaining a sufficiently high feed rate in an extruder although the method is suitable for obtaining a fine powder of the resin in the form of precipitates.